Portable navigation devices (PNDs) that include GPS (Global Positioning System) signal reception and processing functionality are well known, and are widely employed as in-car or other vehicle navigation systems.
In general terms, a modern PND comprises a processor, memory (at least one of volatile and non-volatile, and commonly both), and map data stored within said memory. The processor and memory cooperate to provide an execution environment in which a software operating system may be established, and additionally it is commonplace for one or more additional software programs to be provided to enable the functionality of the PND to be controlled, and to provide various other functions.
Typically these devices further comprise one or more input interfaces that allow a user to interact with and control the device, and one or more output interfaces by means of which information may be relayed to the user. Illustrative examples of output interfaces include a visual display and a speaker for audible output. Illustrative examples of input interfaces include one or more physical buttons to control on/off operation or other features of the device (which buttons need not necessarily be on the device itself but could be on a steering wheel if the device is built into a vehicle), and a microphone for detecting user speech. In a particularly preferred arrangement the output interface display may be configured as a touch sensitive display (by means of a touch sensitive overlay or otherwise) to additionally provide an input interface by means of which a user can operate the device by touch.
Devices of this type will also often include one or more physical connector interfaces by means of which power, and optionally data signals, can be transmitted to and received from the device, and optionally one or more wireless transmitters/receivers to allow communication over cellular telecommunications and other signal and data networks, for example Wi-Fi, Wi-Max GSM and the like.
PND devices of this type also include a GPS antenna by means of which satellite-broadcast signals, including location data, can be received and subsequently processed to determine a current location of the device.
The PND device may also include electronic gyroscopes and accelerometers which produce signals that can be processed to determine the current angular and linear acceleration, and in turn, and in conjunction with location information derived from the GPS signal, velocity and relative displacement of the device and thus the vehicle in which it is mounted. Typically such features are most commonly provided in in-vehicle navigation systems, but may also be provided in PND devices if it is expedient to do so.
The utility of such PNDs is manifested primarily in their ability to determine a route between a first location (typically a start or current location) and a second location (typically a destination). These locations can be input by a user of the device, by any of a wide variety of different methods, for example by postcode, street name and house number, previously stored “well known” destinations (such as famous locations, municipal locations (such as sports grounds or swimming baths or other points of interest), and favourite or recently visited destinations.
Typically, the PND is enabled by software for computing a “best” or “optimum” route between the start and destination address locations from the map data. A “best” or “optimum” route is determined on the basis of predetermined criteria and need not necessarily be the fastest or shortest route. The selection of the route along which to guide the driver can be very sophisticated, and the selected route may take into account historical, existing and/or predicted traffic and road information.
In addition, the device may continually monitor road and traffic conditions, and offer to or choose to change the route over which the remainder of the journey is to be made due to changed conditions. Real time traffic monitoring systems, based on various technologies (e.g. mobile phone data exchanges, fixed cameras, GPS fleet tracking) are being used to identify traffic delays and to feed the information into notification systems.
PNDs of this type may typically be mounted on the dashboard or windscreen of a vehicle, but may also be formed as part of an on-board computer of the vehicle radio or indeed as part of the control system of the vehicle itself. The navigation device may also be part of a hand-held system, such as a PDA (Portable Digital Assistant) a media player, a mobile phone or the like, and in these cases, the normal functionality of the hand-held system is extended by means of the installation of software on the device to perform both route calculation and navigation along a calculated route.
Route planning and navigation functionality may also be provided by a desktop or mobile computing resource running appropriate software. For example, an on-line route planning and navigation facility is provided at routes.tomtom.com, which facility allows a user to enter a start point and a destination, whereupon the server to which the user's PC is connected calculates a route (aspects of which may be user specified), generates a map, and generates a set of exhaustive navigation instructions for guiding the user from the selected start point to the selected destination. The facility also provides for pseudo three-dimensional rendering of a calculated route, and route preview functionality which simulates a user travelling along the route and thereby provides the user with a preview of the calculated route.
In the context of a PND, once a route has been calculated, the user interacts with the navigation device to select the desired calculated route, optionally from a list of proposed routes. Optionally, the user may intervene in, or guide, the route selection process, for example by specifying that certain routes, roads, locations or criteria are to be avoided or are mandatory for a particular journey. The route calculation aspect of the PND forms one primary function, and navigation along such a route is another primary function.
During navigation along a calculated route, it is usual for such PNDs to provide visual and/or audible instructions to guide the user along a chosen route to the end of that route, i.e. the desired destination. It is also usual for PNDs to display map information on-screen during the navigation, such information regularly being updated on-screen so that the map information displayed is representative of the current location of the device, and thus of the user or user's vehicle if the device is being used for in-vehicle navigation.
An icon displayed on-screen typically denotes the current device location, and is centred with the map information of the current road and surrounding roads in the vicinity of the current device location and other map features also being displayed. Additionally, navigation information may be displayed, optionally in a status bar above, below or to one side of the displayed map information, examples of navigation information include a distance to the next deviation from the current road required to be taken by the user, the nature of that deviation possibly being represented by a further icon suggestive of the particular type of deviation, for example a left or right turn. The navigation function also determines the content, duration and timing of audible instructions by means of which the user can be guided along the route. As can be appreciated a simple instruction such as “turn left in 100 m” requires significant processing and analysis. As previously mentioned, user interaction with the device may be by a touch screen, or additionally or alternately by steering column mounted remote control, by voice activation or by any other suitable method.
A further important function provided by the device is automatic route re-calculation in the event that: a user deviates from the previously calculated route during navigation (either by accident or intentionally); real-time traffic conditions dictate that an alternative route would be more expedient and the device is suitably enabled to recognize such conditions automatically, or if a user actively causes the device to perform route re-calculation for any reason.
Although the route calculation and navigation functions are fundamental to the overall utility of PNDs, it is possible to use the device purely for information display, or “free-driving”, in which only map information relevant to the current device location is displayed, and in which no route has been calculated and no navigation is currently being performed by the device. Such a mode of operation is often applicable when the user already knows the route along which it is desired to travel and does not require navigation assistance.
Devices of the type described above provide a reliable means for enabling users to navigate from one position to another.
Often navigation devices are arranged to calculate a route to a destination in a manner that takes into account current conditions in the network, e.g. taking into account congestion. A fastest route may be generated for navigation in this manner. Once navigation commences, traffic conditions may change, such that the route is no longer the fastest route. In this situation, a new fastest route taking into account the actual traffic situation may be generated and proposed to a user. This may be as a result of a continual background check for faster routes under current conditions carried out, e.g. by a PND as navigation progresses, or might be in response to receiving a message indicative of a traffic event on the route ahead, e.g. via a live feed. Such methods are responsive to actual traffic conditions, simply providing a new faster route when the existing route is no longer the fastest route.
The use of vehicle-based navigation devices of various types is becoming more prevalent. For example, navigation devices, including mobile devices, such as PNDs, and integrated systems, e.g. in-dash systems, are increasingly being used in vehicles. However, this may lead to problems when the navigation devices are arranged to take into account real-time traffic information when planning routes. When multiple vehicles travelling in or toward an area affected by congestion use such devices, each device may suggest an alternative route to the driver of its respective vehicle in the manner described above, to enable the driver to avoid the congested area. However, if each device is acting on similar congestion information, and calculates routes in a similar manner, e.g. to provide a new fastest route, the devices will tend to divert drivers onto similar alternative routes. This may have the effect that, rather than reducing overall levels of congestion in the network, the congestion is merely shifted to a different location, i.e. along the alternative routes suggested to drivers. This effect may be particularly significant when a major event, such as a major road closure or obstruction is involved.
Various attempts have been made to address this problem, and to try to cause navigation devices associated with different vehicles to calculate alternative routes in the event of congestion which will result in traffic load being spread over the road network in a more uniform manner. One technique involves using a central server to balance traffic flow across a road network. When a navigation device needs to calculate a route, e.g. in response to congestion being found on an existing route or otherwise, the device sends a route request to the server. The server receives such route requests from multiple devices, and determines routes specifically for the individual devices, and transmits the routes to the respective devices. The routes for the different devices are determined in a manner that is intended to distribute flow more evenly across the road network. In order to achieve this, when a new route is calculated, it is done so in such a way that it is dependent upon previous routes calculated for other navigation devices. Indeed, in some cases, routes for all navigation devices are recalculated whenever a new route request is received. This solution is therefore computationally intensive, and difficult to scale. One example of such a solution is the system proposed and developed by Graphmasters—www.graphmasters.net; formerly known as the Greenway app and which was presented as part of the Microsoft Imagine Cup 2012. Another technique of this type was created as part of a project entitled “Algorithms for Optimal Route Guidance” performed by Technische Universität Berlin with support from DaimlerChrysler—http://www3.math.tu-berlin.de/coga/projects/traffic/routeguidance/, and which aims to distribute traffic flow in a manner that minimises overall travel time of all users through the network.
The Applicant has realised that there remains a need for improved and more efficient methods for generating routes in a navigable network, which try to balance traffic flow across the network.